The Senate so vigorously opposes the Space Corps proposal that it adopted by unanimous consent an amendment — offered by Sens. Bill Nelson and Tom Cotton, shown here in 2016 — to the Senate NDAA that would block it. (Bill Clark/Roll Call)

The House on Thursday agreed by unanimous consent to begin negotiations with the Senate on the fiscal 2018 Defense authorization bill. Throughout the coming weeks, a panel of conferees from each chamber will negotiate a final version of the legislation before Congress votes to send the bill to the president.

The House will send to the conference 46 Republicans and 27 Democrats. Eighteen Republicans and 13 Democrats will represent the Armed Services Committee in the negotiations.

The House committees on Intelligence, Budget, Education and Workforce, Energy and Commerce, Financial Services, Foreign Affairs, Judiciary, Natural Resources, Oversight, Science, Space and Technology, Small Business, Transportation, Veterans Affairs, and Ways and Means will be represented by two Republicans and one Democrat from each committee.

The Senate has not yet named its conference members.

Although the annual Pentagon policy bill has passed Congress each of the past 55 years, the two chambers still have many issues to work through before sending an agreed-upon bill to the president’s desk.

Perhaps the biggest gap between the House and Senate versions of the authorization bill, commonly referred to as the National Defense Authorization Act, or NDAA, is a House provision that would stand up Space Corps, a new military service branch that would focus entirely on space operations, but be under the Air Force’s purview.

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The Senate so vigorously opposes Space Corps that it adopted by unanimous consent an amendment to the Senate NDAA offered by Arkansas Sen. Tom Cotton and Florida Sen. Bill Nelson that blocks any Defense Department spending on the proposed service branch.

The two chambers, however, are closer on other outstanding issues. Both the House and Senate want the Army to add troops, but disagree on how many. The House bill calls for an increase of 17,000 troops to the existing active duty, Army Reserve and National Guard, while the Senate is seeking a more modest increase of 6,000 soldiers.

There is also distance between the chambers in how many of Lockheed Martin’s new F-35 fighter jets the Pentagon should procure. The House wants to authorize Pentagon funds for 87 new jets, 17 more than President Donald Trump’s budget request. The Senate, however, wants 94 F-35s, which run around $100 million per jet.

The problem limiting these expensive military purchases is the nagging issue of budget caps. The 2011 budget law caps base annual defense spending at $549 billion. The House and Senate this year authorized $688.5 billion and $692 billion, respectively, in their versions of the NDAA, way above the budget caps.

“We have to figure out how much money we have,” Rep. Adam Smith of Washington, the top Democrat on the House Armed Services Committee, said.

Typically, conferees have resolved the issue of bypassing budget caps by stashing money in the Overseas Contingency Operations account used to fund foreign conflicts. Such accounts are separate from the “base” normal Pentagon budget.